Computer Batteries

Did you ever wonder how mobile communication devices like personal digital assistants (PDAs), cellular phones and laptops operate while being used by people who move about from place to place? Sure, these devices use batteries but not the kind of battery you have in mind. They use a special type of battery called Lithium-ion (Li-ion).

Gilbert N. Lewis pioneered Li-ion batteries in 1912. The first non-rechargeable cells were created in the early 1970s. The Li-ion battery required nearly 20 years of development before it was safe enough to be used on a mass market level. The first commercial version was created by Sony in 1991, following research by a team led by John B. Goodenough.

Li-ion batteries are often lighter because they have a higher charge density. They are small and mobile, and are more readily stored than hydrogen. Thus, a battery based on lithium is smaller than one with hydrogen elements, such as nickel metal hydride (NMH) or nickel-cadmium (NiCd), and has fewer volatile gases.

The li-ion battery does not degrade when it’s being recharged while at the same time being used in a product. It is capable of easily regulating back and forth the movement of energy from power cell to power cell. Li-ion batteries do not suffer from the memory effect. They also have a low self-discharge rate compared to NMH and NiCd batteries. Another advantage is that their lifespan remains relatively unaffected if they are kept “plugged in” after they have been fully charged. Other rechargeable batteries may degrade in these circumstances.

At a 100% charge level, a typical Li-ion laptop battery that’s full most of the time at 25 C will irreversibly lose approximately 20% capacity per year. This capacity loss begins from the time it was manufactured, and occurs even when the battery is not being used. Li-ion batteries should be kept cool. Ideally, they are stored in a refrigerator. They will age much faster at high temperatures. Keeping them in very hot places can kill Li-ion batteries.

If the battery is used and fully depleted to 0%, this is called a deep discharge cycle, and this decreases its capacity. Approximately 100 deep discharge cycles leave the battery with about 75% to 85% capacity. When used in laptop computers or cellular phones, this rate of deterioration means that after three to five years, the battery will have capacities that are too low to be usable.

Li-ion batteries are not as durable as NiMH or NiCd batteries and can be extremely dangerous if mistreated. They are usually more expensive since they use a newer chemistry and have more advanced applications. Buy Li-ion batteries only when needed. Look at the manufacturing date. That is when the aging process begins.

Li-ion batteries can easily rupture, ignite or explode when exposed to high temperatures or direct sunlight. Short-circuiting a Li-ion battery can also cause it to ignite or explode. Never open a Li-ion battery’s casing. They contain safely devices that, if damaged, can cause the battery to ignite or explode.
A.C.Mendoza Jr.